Apex sealing means



y 25, 1965 HANNS-DIETER PASCHKE 3,185,387

APEX SEALING MEANS Filed March 14, 1963 2 Sheets-Sheet 1 HANNE-DETER E XEHKE ATTORNEY y 1965 HANNS-DIETER PASCHKE 3,185,387

APEX SEALING MEANS Filed March 14, 1965 2 Sheets-Sheet 2 INVENTOR.HANNEI-DIETER F'AEILJHKE.

BY f 773mm (0. ATTEIRNEW United States Patent 2 Claims. oi. 230-445 Thepresent invention relates broadly to the art of rotary mechanisms and isparticularly directed to sealing means for such rotary mechanisms.

The invention is particularly useful in connection with rotarymechanisms similar to that disclosed in United States Patent Number2,988,065, although as will become apparent, this invention is notlimited to this specific type of rotary mechanism. In the followingdescription the invention is described in relation to an internalcombustion engine, but the invention .is also suitable to other forms ofrotary mechanisms such as fluid pumps and fiuid motors.

A rotary engine as disclosed in said patent comprises an outer body orhousing having a cavity therein and an inner body or rotor disposedtherein rotatable relative to the outer body, about an axis laterallyspaced from, but parallel to the axis of said cavity. The inner body isjournaled on an eccentric portion of a shaft which is co-axial with theouter body and journaled in bearings carried by the outer body endWalls. The outer body has axially-spaced end walls and a peripheral wallinterconnecting the end walls to form said cavity; the inner surface ofthe cavity peripheral wall having a multi-lobed profile which preferablyis basically an epitrochoid.

The inner body or rotor has end faces carrying end-face seal means andintermediate seal elements disposed adja cent to said outer body endwalls for sealing cooperation therewith, and has a peripheral surfacewith a plurality of circumferentialiy-spaced apex portions, eachcarrying a radially-movable seal for sealing engagement with themulti-lobed inner surface of the outer body peripheral wall to form aplurality of working chambers between the two bodies which vary involume upon relative rotation of the two bodies.

Each apex seal of the inner body is received within an outwardly-facinggroove running axially from one end face to the other of the inner bodyat its associated apex portion on the inner body thereby separating theadjacent Working chambers. Each apex seal fits within its apex groovewith a clearance between the apex seal side faces and the groovesidewalls so that the apex seal is radially movable. The operatingpressures in the working chambers are difierent from one another so thatthere is a differential pressure across each apex seal between each twoadjacent chambers which urges the apex seal against one side wall andaway from the opposite side wall of its apex groove. Gas from thechamber with the higher pressure enters the bottom of the apex groovethrough the gap between the apex seal side face and apex groove sidewall which are adjacent to said chamber. The gas pressure urges saidapex seal against the opposite apex groove side' wall adjacent to theworking chamber with the lower pressure and also urges the apex sealradially outwardly so that its outer edge is in sealing engagement withthe peripheral wall inner surface.

Prior combustion engines of this type have apex seals which arerectangularin their cross-section and with a uniform thickness measuringonly a small fraction of the radial height of the apex seal so that thepressure of the operative medium on the underside of the apex seal maynot be sufficient to urge the apex seal radially outwardly counter tothe frictional force acting between the side face of the apex seal andits adjacent groove sidewall; Hence, in such prior engines it may benecessary to add relatively strong spring means under the apex sealwhereby the wear of the radially outer edge of the apex seal isincreased.

An object of the present invention comprises the provision of a rotarycombustion engine in which a novel apexrseal arrangement for the workingchambers is provided to maintain continuous and improved sealing duringengine operation.

Specifically, instead of providing apex seals of uniform thickness, thisinvention provides apex seals with recesses on both side faces in theregion within their apex grooves, with the recesses in opposite sidefaces of each apex seal communicating with one another.

Other objects of the invention will become apparent upon reading theannexed detail description in connection with the drawings in which:

FIG. 1 is a schematic, transverse, sectional view of a rotary combustionengine;

FIG. 2 is a partial, longitudinal, sectional view through the rotor apexportion and groove showing to a greatly enlarged scale the apex seal inaccordance with the invention;

FIG. 3 is a cross-sectional view, as taken on line 33 of FIG. 2;

FIG. 4 is a cross-sectional view, as taken on line 4-4 of FIG. 2;

FIG. 5 is a perspective view of an end portion of the rotor apex portionwith the apex seal omitted;

FIG. 6 is a view similar to that of FIG. 3 with the spring omitted andshowing an additional form of apex seal in accordance with theinvention.

Referring to the drawings, the housing or outer body of a rotarycombustion engine comprises spaced end walls 10 and 12, and a peripheralWall 14 disposed between the interconnecting said end walls to form acavity therebetween. The inner surface 16 of the peripheral wall 14preferably has a multi-lobed profile in cross section which preferablyis basically an epitrochoid.

Inside and eccentric to the housing is disposed an inner body or rotor18, having a plurality of circumferentiallyspaced apex portions 20 aboutits outer periphery to form a plurality of working chambers 32 betweenthe inner and outer bodies which vary in volume upon rotation of theinner body relative to the outer body.

Each of said apex portions 20 has radially-movable apex seal strip means22 received within a single outwardly-facing groove 24 extending in adirection parallel to the rotor axis from one end face to the other ofthe rotor 18 and urged radially outward by spring means 26 and by gaspressure from the adjacent working chamber having the higher pressureinto sealing engagement with the peripheral wall inner surface.

The inner body 18 also has end faces having end-face seal means 28 andintermediate seal elements 30 disposed in sealing engagement with theend walls 10 and 12 which together with the apex seals 22 form acontinuous seal about the working chambers 32.

The bottom of each apex groove 24 has an enlarged cylindrical boreportion at each end of the groove, and an axially-movable intermediateseal element 30 is slidably fitted within such cylindrical bore portionand urged axially against the adjacent end wall 16 or 12 by gas pressurewithin said groove. means 22 is in sealing cooperation with anintermediate seal element 30. Between the intermediate seal elements 30,disposed at the rotor apex portions 20 on each end face of the rotor 18adjacent to the rotor periphery are end face seal strips 28, each ofwhich extends from one Each end of the apex sealv intermediate sealelement 30 to an adjacent element 30 and is received in a groove 24 inits rotor end face.

During rotation of the inner body 18, the apex seal means 22 slidecontinuously along their outer edges in bearing against the innersurface 16 of the peripheral wall 14 and the intermediate seal elements30 and end-face seal strips 28 slide continuously along the flat innersurfaces of the end walls and 12.

During engine operation, the working chambers 32 have varying gaspressures. The pressure differential between each two adjacent workingchambers 32 urges the apex seal strip 22 therebetween laterally towardone side face or the other of its grooves 24 for sealing engagementtherewith thereby leaving a slight clearance 33 (FIG. 3) at the otherside face of said groove. As a result, gas pressure from the adjacentworking chamber is transmitted through said clearance 33 into the bottomof the associated groove 24 whereby said pressure urges the twointermediate seal members at the ends of said groove axially intosealing engagement with the end walls 10 and 12 of the outer body andalso adds to the force of the spring 26 urging said apex seal strip 22radially outwardly.

The pressure differential urges the apex seal 22 in hearing against thesidewall 34 or 36 of the apex groove 24, and also causes a frictionalforce which acts counter to the forces on the apex seal 22 urging theapex seal radially outwardly against the peripheral wall 14.

The engine so far described is substantially similar to the enginedisclosed in the aforementioned United States Patent Number 2,988,065and for additional description reference is made to said patent. Theseal arrangement so far described is substantially similar to the sealarrangement disclosed in United States Patent Number 3,033,180 andreference is made to said patent.

The pressure differential acting across each apex seal strip means 22between its two adjacent chambers 32 urges said apex seal toward thechamber with the lower pressure, pressing the seal face in bearingagainst the adjacent groove side wall. According to the invention, asillustrated in FIG. 2, both side faces 38 and of each apex seal 22 arerespectively provided with recesses 42 and 44 in the region within itsapex groove 24. The recessed portions 42 and 44 of the two seal facesare in communication with each other, preferably through openings 46 ineach said apex seal 22, so that the contact pressure and frictionbetween the contacting side face 38 or 40 of each said apex seal 22 andthe contacted sidewall 34 or 36 of its apex groove 24 is reduced wherebyeach said apex seal 22 can move toward the inner surface 16 of theperipheral wall 14. As the frictional force equals the product of thepressure-impinged area, the pressure on said area and the coefficient offriction; the frictional force is minimized by providing recesses 42 and44 in the side faces 38 and 40 of each said apex seal 22 which are incommunication with one another. Thus, the pressure acting on one sideface 33 in the region of its recess 42 is annulled by the equal pressureacting on the opposite side face 40 of each said apex seal 22 in theregion of its recess 44. The recesses 42 or 44 leaves ridges 48 or 50about the recesses on the side faces 38 or 40 of the apex seals 22. Eachsaid ridge 48 and 50 is a raised portion of its side face 38 or 40 witha preferably flat surface in contact with its adjacent groove sidewall34 or 36 whereby the contacting area of said ridge 48 or 50 becomes thesole pressure-impinged area. Each ridge or raised portion 48 or 50 formsa border around its recess 42 or 44 and covers the edge or corner of theapex groove 24 in order to seal off one chamber from its adjacentchamber 32.

The recesses 42 and 44 extend to the radially inner edge of each saidapex seal strip 22, as illustrated in FIG. 1, whereby the recesses 42and 44 on opposite side faces 38 and 40 of each said apex seal 22 may bein communication with each other. In addition, however, openings orapertures 46 are preferably also provided in the apex seal strip 22communicating with said recesses 42 and 44,

thereby providing a more rapid equilibrium of the gas pressures onopposite side faces 38 and 40 of the apex seal 22 in the region of theirrecesses 42 and 44. The number and size of the openings 46 in each apexseal strip 22 are such that the cross-sectional area of the openingprovided thereby between the recesses 42 and 44 is sufficient relativeto the size of the recesses 42 and 44 to provide for rapid equalizationof the pressures in said recesses without said openings causing undueweakening of the apex seal strip 22.

As illustrated in FIG. 2, the radial depth of the portion of each apexgroove 24 between the bores for the intermediate seal elements 30preferably is made less than the radial depth at said seal elements.This construction serves to minimize the volume of each apex groove 24so that the pressure below each apex seal strip 22 is able to morerapidly conform to pressure variations, particularly the pressurevariations in the adjacent working chamber 32 having the higherpressure.

Considering the forces acting on each said apex seal strip 22, byanalogy, each said seal strip 22 may be regarded as a two-armed leverhaving a fulcrum formed by the outer corner 52 of its apex groovesidewall 34 or 36 against which the apex seal 22 bears. The gas forcesthat act on the portion of the apex seal strip 22 extending outside ofits apex groove 24 tend to tip the strip 22 about said groove corner 52;while the gas forces that act on the portion of the apex seal strip 22within its apex groove 24 act counter to said tipping forces. In orderto minimize any such tipping of an apex seal strip 22, the portion ofthe surface area of each side face of an apex seal strip bounded by theridges 48 or 50, other than the surface area of the recesses 42 or 44,and which is disposed within its apex groove 24 is so formed and shapedthat each of these surface portions has a substantial surface area withthe center of area of each said surface portion having a substantialmoment arm from the groove outer edge such that the turning moment ofthe gas forces on said surface area portions of an apex seal strip isgreater than the opposing turning moment of the gas forces on theportion of the apex seal strip disposed outside its apex groove 24 andtending to tip the seal about the outer edge of said groove.

In some regions of the inner surface 16 of the peripheral wall 14, thereis a frictional force between the seal strip outer edge or crest 54 andsaid inner surface 16 which acts together with the forementioned forcesand causes a tilting of each said apex seal strip 22. Such a frictionalforce, which is represented by the arrow, and letter P in FIG. 3, isopposite to the direction in which the inner body 18 is turning asindicated by the arrow, and letter D.

In order to increase the moment acting counter to such tipping forcesand to avoid any such tipping of the apex seal strip 22, a substantialportion of each ridge 48 and 50 is preferably disposed near the radiallyinner portion of its apex seal strip 22 so that the pressure-impingedarea of the contacting ridge surface has a lever arm which is as long aspossible whereby its countertilting moment is as large as possible. Withsuch a shape to the ridges 48 and 50 at each side face 38 and 40 of eachsaid apex seal 22, the center of gravity of its pressureimpinged area isas far as possible from the corner 52 of its groove side wall 34 or 36and its counter-tilting moment is as large as possible.

As illustrated in FIG. 5, the inner body 18 preferably has a cut-outgroove 56 in each end portion of each apex groove 24 runningsubstantially normal to said apex groove. In addition, each said apexseal strip 22 preferably has a pocketlike recess 58 in each side face 38and 40 of the apex seal strip 22 adjacent said cut-out groove 56 asillustrated in the left side of FIG. 2. The pocketlike recess 53together with the gap 60 between the rotor end face and the housing endwall 10 or 12 in FIG. 4, or the cut-out groove 56 in FIG. 5. form acontinuous passage to vent the region adjacent to said pocketlike recess58 to i the working chamber 32 with the lower gas pressure,

thereby providing improved bearing of the ridge 48 or 50 against the endportions of the groove side wall 34 or 36. In FIG. 6, the outer crestor'edge 54a of the apex seal strip 22a is formed by a tenon-likeextension 62, or tonguelike protrusion on the apex seal strip 22, whichcontacts For ease of understanding, the parts of FIG. 6 corresponding tothe parts of FIGS. 1 through 5 have been designated by the samereference numerals but with a subscript -a added thereto. On each sideof the tenon-like extension 62, the apex seal strip 22a has a cut-backstep whereby there is always a portion A of the overall width of theapex seal strip 22a, which is exposed to that adjacent chamber 32ahaving the lower pressure. Thus, there is a residual area against whichthe gas pressure can act to force the seal strip 22a radially outwardly.

As illustrated in FIG. 6, the higher gas pressure in one chamber 32aurges the apex seal strip 22a against the groove sidewall 36a adjacentto the chamber 32a with the lower gas pressure. The higher gas pressureacts against the underside 64a of the seal strip 22a, and against theside face 33a of the seal strip 22a adjacent to the higher pressurechamber 31a and also against the portion of the outerside area which ison the high pressure side of the line of contact. The gas pressure on aportion of the underside area is annulled by the similar gas pressure ona corresponding outerside area. However, the lower gas pressure acts onanother portion indicated by the width A of the outerside area, which ison the low pressure side of the line of contact. Hence, in all regionsof the peripheral-wall inner surface 16a, the apex seal 22a has aresidual portion of the underside area, which is opposite to thelow-pressure portion A of theouterside area, against which the gaspressure acts to force the seal strip 22a radially outwardly. Moreover,with such construction of the apex seal strip 22a, as illustrated inFIG. 6, the spring is preferably omitted as the gas pressure on theunderside 64a of the apex strip 22a overcomes the counteracting frictionat the groove sidewall 36a, and forces the apex seal strip 22a radiallyoutwardly.

While I have described my invention in detail in its present preferredembodiment it will be obvious to those skilled in the art afterunderstanding my invention that various changes and modifications may bemade therein without departing from the spirit or scope thereof. It isintended by the appended claims to cover all such modifications.

What is claimed is:

1. A rotary mechanism comprising an outer body having spaced end wallsand a peripheral wall forming a cavity therebetween; an inner bodyhaving axially-spaced end faces and disposed within said outer bodycavity between the end walls thereof for rotation relative to said outerbody with each of said end faces adjacent to an end wall; said innerbody having a plurality of circumferentially-spaced apex portions havingsealing cooperation with the inner surface of the peripheral Wall ofsaid cavity to form between the inner and outer bodies a plurality ofworking chambers wherein varying fluid pressures cyclically occur; and aplurality of seal strips, one for each of said apex portions and eachreceived in a groove in an apex portion extending from one end face tothe other of the inner body; each said seal strip having a width in thecircumferential direction which is slightly less than the width of itsassociated groove whereby the fluid in that one of the two adjacentworking chambers having the higher pressure urgesv said seal stripagainst the opposite side of its groove and enters the groove and actson the radially inner edge ofthe seal strip to urge it radially outwardinto sealing engagement with the inner surface of the outer bodyperipheral wall; each said seal strip having at least one recess in eachof its side faces disposed within a region of said side face which isdisposed entirely within its apex portion groove, said recess extendingover a substantial area of said side face, the recesses on oppositesides of said seal strip being of substantially equal area, said sealstrip having at least one passage therethrough interconnecting saidrecesses; each of said seal strips having an additional recess in eachof its side faces adjacent at least one end of said strip, each saidadditional recess being disposed inwardly of the outer edge of theassociated groove for said seal strip and extending to said adjacent endof said seal strip.

2. The combination recited in claim 1, wherein the end face of saidinner body adjacent saidadditional recesses in said seal strip isslightly out back in the axial direction in the apex region to vent saidadditional recesses to the adjacent working chambers.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS22,712 of 1911 Great Britain. 732,394 6/55 Great Britain.

JOSEPH H. BRANSON, JR., Primary Examiner.

Davin l03135

1. A ROTARY MECHANISM COMPRISING AN OUTER BODY HAVING SPACED END WALLSAND A PERIPHERAL WALL FORMING A CAVITY THEREBETWEEN; AN INNER BODYHAVING AXIALLY-SPACED END FACES AND DISPOSED WITHIN SAID OUTER BODYCAVITY BETWEEN THE END WALLS THEREOF FOR ROTATION RELATIVE TO SAID OUTERBODY WITH EACH OF SAID END FACES ADJACENT TO AN END WALL; SAID INNERBODY HAVING A PLURALITY OF CIRCUMFERENTIALLY-SPACED APEX PORTIONS HAVINGSEALING COOPERATION WITH THE INNER SURFACE OF THE PERIPHERAL WALL OFSAID CAVITY TO FORM BETWEEN THE INNER AND OUTER BODIES A PLURALITY OFWORKING CHAMBERS WHEREIN VARYING FLUID PRESSURES CYCLICALLY OCCUR; AND APLURALITY OF SEAL STRIPS, ONE FOR EACH OF SAID APEX PORTIONS AND EACHRECEIVED IN A GROOVE IN AN APEX PORTION EXTENDING FROM ONE END FACE TOTHE OTHER OF THE INNER BODY; EACH SAID SEAL STRIP HAVING A WIDTH IN THECIRCUMFERENTIAL DIRECTION WHICH IS SLIGHTLY LESS THAN THE WIDTH OF ITSASSOCIATED GROOVE WHEREBY THE FLUID THAT ONE OF THE TOW ADJACENT WORKINGCHAMBERS HAVING THE HIGHER PRESSURE URGES SAID SEAL STRIP AGAINST THEOPPOSITE SIDE OF ITS GROOVE AND ENTERS THE GROOVE AND ACTS ON THERADIALLY INNER EDGE OF THE SEAL STRIP TO URGE IT RADIALLY OUTWARD INTOSEALING ENGAGEMENT WITH THE INNER SURFACE OF THE OUTER BODY PERIPHERALWALL; EACH SAID SEAL STRIP HAVING AT LEAST ONE RECESS IN EACH OF ITSSIDE FACES DISPOSED WITHIN A REGION OF SAID SIDE FACE WITH IS DISPOSEDENTIRELY WITHIN ITS APEX PORTION GROOVE, SAID RECESS EXTENDING OVER ASUBSTANTIAL AREA OF SAID SIDE FACE, THE RECESSES ON OPPOSITE SIDES OFSAID SEAL STRIP BEING OF SUBSTANTIALLY EQUAL AREA, SAID SEAL STRIPHAVING AT LEAST ONE PASSAGE THERETHROUGH INTERCONNECTING SAID RECESSES;EACH OF SAID SEAL STRIPS HAVING AN ADDITIONAL RECESS IN EACH OF ITS SIDEFACES ADJACENT AT LEAST ONE END OF SAID STRIP, EACH SAID ADDITIONALRECESS BEING DISPOSED INWARDLY OF THE OUTER EDGE OF THE ASSOCIATEDGROOVE FOR SAID SEAL STRIP AND EXTENDING TO SAID ADJACENT END OF SAIDSEAL STRIP.